Hypoalbuminemia is the strongest predictor of death in patients with renal failure. We planned to investigate the factors influencing serum albumin levels in continuous ambulatory peritoneal dialysis (CAPD) patients. We prospectively followed 100 CAPD patients for 18.6 +/- 12.8 months. The parameters searched for a correlation with serum albumin levels were: peritoneal transport kinetics; presence of nephrotic syndrome; biochemical parameters; anthropometric measurements; and subjective global assessment (SGA). Older patients (age > or = 60 years), patients with diabetes mellitus or amyloidosis, high and high-average transporters, and those with nephrotic syndrome had significantly lower albumin levels throughout the follow-up. In addition, significantly lower albumin levels were found in patients who were in the SGA "malnourished" categories and those who had iPTH levels < or = 65 pg/mL. Albumin level was negatively correlated with age, C-reactive protein (CRP), and fibrinogen level; it was positively correlated with total cholesterol, intact parathyroid hormone (iPTH) level, and triceps skin-fold thickness. By regression analysis, age [risk ratio (RR): 0.2437], presence of diabetes mellitus (RR: 0.1421) and high or high-average transport status (RR: 0.1156) were independent predictors of hypoalbuminemia (< or = 3.5 g/dL). In conclusion, development of hypoalbuminemia is multifactorial in CAPD patients. Older age, cause of renal failure, transport status, chronic inflammation, presence of nephrotic syndrome, and nutrition status are important determinants of hypoalbuminemia.